The present invention relates to waste treatment method and waste treatment apparatus capable of effectively obtaining an energy from an industrial waste and municipal or domestic waste particularly by utilizing a technology for improving gasification treatment function and efficiency.
Waste is largely classified into municipal or domestic waste including household waste, so-called urban waste, and industrial waste.
These wastes include various sectors of materials such as paper, fiber, wood, bamboo, rubber, metal, plastic, glass, pottery, soil, sand and the like. A calorific value (heating value) of these wastes is generally calculated to be 4000-5000 kcal on dry basis excluding water content, which corresponds to about 2/3 of the heating value of coal. Therefore, it is considered that the waste is a large energy source.
Recently, various waste treatment (disposal) methods for obtaining energy from the waste have been developed.
For example, Japanese Patent Laid-Open Publication No. HEI 8-24904 and Japanese Patent Laid-Open Publication No.HEI 9-79548 disclose a waste treatment (disposal) method and waste treatment apparatus relating to the waste treatment method.
FIG. 6 is a diagram showing a structure of a conventional waste treatment apparatus.
As shown in FIG. 6, the waste treatment apparatus essentially comprises a pyrolysis (thermal decomposition) unit 4 for pyrolysing waste 1 as raw material into pyrolysis gas 2 and solid material 3, and a mechanical processing unit 5 for crushing the solid material 3 obtained by this pyrolysis unit 4 to fine particles so as to separate metal contained in the solid material 3, which are processing units on an initial stage. Further, a high temperature gasification unit 10 for converting a pyrolysis char 6 obtained by the mechanical processing unit 5 and pyrolysis gas 2 obtained by the pyrolysis unit 4 to heating gas 9 of low molecular carbide by adding oxidizer 7 and production control char 8 like coke is provided at the post stage.
The pyrolysis unit 4 is provided with a shredder 11 for crushing the waste 1 to fine particles and on the other hand, a secondary side of the high temperature gasification unit 10 is provided with a gas scrubber 12 for removing HCl, HF and dirt. Then, an energy utilization unit 13 for supplying the heating gas 9 and a flue gas desulfurization plant 15 for desulfurizing flue gas 14 are provided on the secondary side of the gas scrubber 12.
A waste treatment method for treating the waste using the apparatus of the structure mentioned above will be described hereunder.
That is, after the waste 1 essentially consisting of metallic dirt to which organic substance adheres is crushed to fine particles with the shredder 11, air 16 and energy 17 are supplied to the pyrolysis unit 4, which is actuated at a temperature of about 550-600.degree. C. so as to separate the pyrolysis gas 2 and solid material 3. This solid material 3 is crushed by the mechanical processing unit 5, and metal 18 contained in the solid material 3 is sorted and the metal 18 is removed after washing. On the other hand, after the metal 18 is removed, the pyrolysis char 6 essentially consisting of pyrolysed organic substance and inorganic component is introduced to a high temperature gasification unit 10 together with the pyrolysis gas 2.
The high temperature gasification unit 10 is operated by supplying an oxidizer 7 and an energy 19 at 1600.degree. C. so as to convert the pyrolysis char 6 and pyrolysis gas 2 to a low molecular heating gas 9. In this high temperature gasification unit 10, the inorganic component is converted to part of glass structure 20 through a heating process, and the inorganic component is then removed.
After dirt contained in the heating gas 9 is removed in the gas scrubber 12, the heating gas 9 is introduced to the energy utilization 13. Further, the flue gas 14 generated from the energy utilization unit 13 and exhaust gas 21 generated from the pyrolysis unit 4 are introduced into the flue gas desulfurization plant 15 so as to obtain a low temperature clean exhaust gas 22.
A part of gas 23 purified by removing dirt in the gas scrubber 12 is supplied to the pyrolysis unit 4. Further, an energy 24 obtained in the high temperature gasification unit 10 and energy utilization unit 13 is used for recycle in other plant.
Although the waste treatment method mentioned above is excellent in such a viewpoint that rough particle incombustible component contained in the waste can be used for recycle, the following problems are contained.
Conventionally, the pyrolysis gas 2 generated by carbonization and the pyrolysis char 6 obtained after the mechanical treatment are introduced to the high temperature gasification unit 10 at the same time and, then, a heating gas 9 is obtained by gas conversions of the pyrolysis gas 2 and pyrolysis char 6 in the high temperature gasification unit 10. However, it is difficult to satisfy an optimum condition for treating the pyrolysis gas 2 and pyrolysis char 6 at the same time, and as a result, the heating gas 9 cannot be obtained effectively from the pyrolysis gas 6. That is, there is a problem that gas treatment efficiency is not good.
Further, in the above described conventional waste treatment apparatus, chlorine contained in the waste 1 is combined with oxygen in the pyrolysis unit 4 so that harmful dioxin is generated, which provides a severe problem in viewpoint of environment pollution. Further, because the chlorine and the like are contained in the waste 1, the pyrolysis apparatus is likely to corroded by these materials, so that the apparatus is likely to be deteriorated.
Although, before the heating gas 9 is supplied to the energy utilization unit 13, desulfurization or other treatment is desirable in viewpoint of corrosion of the energy supply unit 13, such a treatment has not been done and therefore, the heating gas 9 obtained from the waste has not been effectively used.